Written by hand.
Test module with a root package added in v1.1.0
and a subpackage added in v1.2.0.

-- .mod --
module example.net/pkgadded

go 1.16
-- .info --
{"Version":"v1.1.0"}
-- go.mod --
module example.net/pkgadded

go 1.16
-- README.txt --
We will add the package example.net/pkgadded/subpkg in v1.2.0.
-- pkgadded.go --
// Package pkgadded was added in v1.1.0.
package pkgadded